Method and device for receiving a subframe in different forms in a wireless communication system

ABSTRACT

The present invention proposes a method for preventing, when two types of subframes (first subframe and second subframe) exist in a wireless communication system, a high version terminal from performing unnecessary operation for the second subframe. Through the present invention, the high version terminal skips unnecessary operation, resulting in reduction of unnecessary power consumption.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system and, inparticular, to an operation method and apparatus of a high version(Rel-10) terminal in case of existence of MBSFN subframe supportingunicast in the high version (Rel-10) network of Long Term Evolution(LTE) system in which terminals with different versions (Releases 8, 9,10, etc.) coexist.

2. Description of the Related Art

With the rapid advance of the wireless communication technology, thecommunication systems have evolved to the 4^(th) Generation mobilecommunication system represented by LTE system. In the LTE system, thedata is transmitted in unit of frame having a length of 10 msec, a frameconsisting of 10 subframes.

FIG. 1 is a diagram illustrating a structure of a downlink frame used inthe LTE system.

In FIG. 1, the frame 101 consists of 10 subframes 103 including normalsubframes 150 carrying normal data and Multimedia Broadcast multicastservice Single Frequency Network (MBSFN) subframes 107. The normal andMBSFN subframes differ from each other in number of Orthogonal FrequencyDivision Multiplexing (OFDM) symbols, length of Cyclic Prefix (CP), andstructure and number of Cell-specific Reference Signal (CRS), and theMBMS subframe is used only for the purpose of transmitting broadcast andmulticast data in Rel-8 and Rel-9 systems. As the system evolves,however, the MBSFN subframe can be used for the purpose of unicasttransmission to a specific terminal as well as broadcast/multicast inthe LTE Rel-10 or later.

For unicast data transmission/reception, the resource allocationinformation indicating the resource allocated for transmission/receptionis carried on the Physical Downlink Control Channel (PDCCH) and the realdata is carried on the Physical Downlink Shared Channel (PDSCH). Theterminal determines whether there is any resource allocation informationaddressed thereto on the PDCCH before attempt receiving real data.

In this case, the LTE Rel-10 terminal has to check the PDCCH carryingthe resource allocation information for the MBSFN subframe in order toreceive PDSCH through even the MBSFN subframe. However, if the LTERel-10 terminal has to check PDCCH in every MBSFN subframe, this maycause unnecessary operation depending on whether the MBSFN subframecarries terminal-specific unicast data or multicast/broadcast data.

DISCLOSURE OF INVENTION Technical Problem

The present invention has been made in an effort to solve this problem,and it is an object of the present invention to provide a method for aterminal to receive data in a situation where different type subframesexist in the wireless communication system including networks operatingwith different versions of LTE.

Solution to Problem

In the case that the new version (Rel-10 or later) terminal is in a newversion network, the terminal receives information on whether PDSCHreception over MBSFN subframe through broadcast or unicast issupportable from the new version network and, if supportable, takesoperation for interpreting PDCCH for receiving PDSCH over MBSFN subframeand, otherwise if not supportable, skips corresponding operation inMBSFN subframe.

Advantageous Effects

In the proposed method, the new version terminal operating in a newversion network reduces unnecessary operation for data reception whenunicast data transmission is not supported in the network, depending onwhether the network supports unicast data transmission in MBSFNsubframe, resulting in reduction of power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of a downlink frame used inthe LTE system;

FIG. 2 is a flowchart illustrating the new terminal procedure in themethod according to an embodiment of the present invention; and

FIG. 3 is a block diagram illustrating the configuration of the terminalaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the following, detailed description of well-known functions andstructures incorporated herein may be omitted to avoid obscuring thesubject matter of the present invention. Exemplary embodiments of thepresent invention are described with reference to the accompanyingdrawings in detail.

In the present invention, the description is directed to the LTE systemfor convenience purpose.

There are several releases of LTE and among them the legacy Rel-8 andRel-9 do not support PDSCH reception in MBSFN subframe. Accordingly, thelegacy terminal does not attempt decoding PDCCH for receiving DownlinkControl Information (DCI) including PDSCH scheduling information forreceiving PDSCH in MBSFN subframe.

In the Rel-10 or later system, however, it is allowed to transmit PDSCHin MBSFN subframe. In this case, unlike the legacy terminal which takesno action for MBSFN subframe because it cannot receive PDSCH in MBSFNsubframe, the new terminal has to take an action for receiving PDSCH toacquire DCI including scheduling information for receiving PDSCH inMBSFN subframe. In the following description, new terminal denotes anLTE Rel-10 terminal, i.e. the terminal capable of receiving PDSCH inMBSFN subframes.

FIG. 2 is a flowchart illustrating the new terminal procedure in themethod according to an embodiment of the present invention.

The new version terminal receives a downlink frame structure in SystemInformation Block broadcast by a base station at step 203. The downlinkframe structure is transmitted in the form of a bitmap indicatingpositions of MBSFN subframes.

Next, the terminal receives information on whether the base stationsupports PDSCH over MBSFN subframe at step 205. The PDSCH over MBSFNsubframe supportability can be broadcasted in the system information ofthe base station or transmitted to the individual terminals throughrespective control messages. The PDSCH over MBSFN subframesupportability information can be transmitted in a Radio ResourceControl (RRC) message explicitly with a newly defined indicator orimplicitly with a legacy information (e.g. predefined channelconfiguration information, transmission mode information, etc.). Steps203 and 250 can be performed in opposite order. In the case of legacynetwork or legacy base station, the supportability information on PDSCHover MBSFN is not transmitted. If no supportability information on PDSCHover MBSFN is received, the UE assumes that the base station does notsupport PDSCH of MBSFN.

If it is determined at step 207 that PDSCH over MBSFN subframe issupported, the UE receives PDCCH including DCI, at step 209, forreceiving PDSCH in MBSFN subframes based on the information received atstep 205.

If it is determined at step 207 that PDSCH over MBSFN subframe is notsupported or if no supportability information on PDSCH over MBSFNsubframe is received, the terminal takes no action for receiving PDSCHin MBSFN subframe. In this case, the terminal does not perform anyoperation for receiving PDSCH.

FIG. 3 is a block diagram illustrating the configuration of the terminalaccording to an embodiment of the present invention.

The terminal communicates data with higher layer 305 andtransmits/receives control messages through a control message processor207. The terminal multiplexes the control signals or data by means ofthe multiplexer/demultiplexer 303 and transmits the multiplex result bymeans of the transceiver 301 under the control of the controller 309.The terminal demultiplexes the physical signal received by thetransceiver 301, by means of the multiplexer/demultiplexer 303, andtransfers the demultiplexed signals to the higher layer 305 or controlmessage processor 307 under the control of the controller 309.

In the present invention, the terminal receives MBSFN subframeconfiguration information broadcasted by the base station and receivesthe supportability information on PDSCH over MBSFN subframe throughbroadcast or unicast. Such a control message is received, the controlmessage processor 307 transfers to the controller 309 the information onwhether each subframe is normal or MBSFN subframe and whether PDSCH overMBSFN subframe is supported in order to determine whether to receivePDCCH for receiving PDSCH at every subframe. That is, if PDSCH overMBSFN subframe is supported, the terminal performs operation forreceiving PDSCH even in MBSFN subframes and, otherwise PDSCH over MBSFNsubframe is not supported, performs no action for receiving PDSCH inMBSFN subframes.

Although the block diagram of the terminal is directed to the case wherethe function blocks are responsible for different functions, the presentinvention is not limited thereto. For example, the controller 309 mayperform the functions of the control message processor 307.

In the proposed method, the network notifies the new version terminalwhether it supports PDSCH over MBSFN subframe so as to avoid unnecessaryreception operation for receiving PDSCH over MBSFN subframe, resultingin reduction of power consumption.

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove with specific terminology, this is forthe purpose of describing particular embodiments only and not intendedto be limiting of the invention. While particular embodiments of thepresent invention have been illustrated and described, it would beobvious to those skilled in the art that various other changes andmodifications can be made without departing from the spirit and scope ofthe invention.

What is claimed is:
 1. A subframe reception method of a terminal in awireless communication system, the method comprising: receiving a systeminformation block including information on downlink frame structure;receiving information on whether a base station supports physicaldownlink shared channel over Multimedia Broadcast multicast serviceSingle Frequency Network (MBSFN) subframe; and receiving, when the basestation supports physical downlink shared channel over MBSFN subframe,physical downlink control channel in the MBSFN subframe.
 2. The methodof claim 1, further comprising skipping, when the base station does notsupports physical downlink shared channel over MBSFN subframe, receiptof physical downlink control channel in the MBSFN subframe.
 3. Themethod of claim 1, wherein receiving information comprises receiving aRadio Resource Control (RRC) message including an indicator indicatingsupportability of physical downlink shared channel over MBSFN subframefrom the base station.
 4. A terminal for receiving subframe transmittedby a base station in a wireless communication system, the terminalcomprising: a transceiver which transmits and receives controlinformation and data to and from a base station; and a controller whichcontrols receiving a system information block including information ondownlink frame structure, receiving information on whether a basestation supports physical downlink shared channel over MultimediaBroadcast multicast service Single Frequency Network (MBSFN) subframe,and receiving, when the base station supports physical downlink sharedchannel over MBSFN subframe, physical downlink control channel in theMBSFN subframe.
 5. The terminal of claim 4, wherein the controllercontrols skipping, when the base station does not supports physicaldownlink shared channel over MBSFN subframe, receipt of physicaldownlink control channel in the MBSFN subframe.
 6. The terminal of claim4, wherein the controller controls receiving a Radio Resource Control(RRC) message including an indicator indicating supportability ofphysical downlink shared channel over MBSFN subframe from the basestation.